Characterization of fatty acid biosynthesis in the cyanobacterium Anabaena variabilis

Abstract

The fatty acid synthetase and elongation systems from Anabaena variabilis were characterized using the 102 000 × g supernatant of cells disrupted using a French pressure cell. The fatty acid synthetase had an absolute requirement for acyl carrier protein and produced fatty acids which were still esterified to the acyl carrier protein. The only other cofactor required for maximal activity of the fatty acid synthetase was NADPH, and the synthetase was inhibited by coenzyme A. Saturated products were myristic, palmitic and stearic acids. The synthetase also produced two long-chain acyl intermediates of the synthetase. The elongation system also was active in the high-speed supernatants of A. variabilis. Myristoyl-acyl carrier protein and palmitoyl-acyl carrier protein were elongated to palmitic and stearic acids, respectively. The elongation system required only NADPH for activity. In addition to studying the fatty acid synthetase and elongase, an attempt was made to measure stearoyl-acyl carrier protein desaturase activity. In either high-speed supernatants or crude homogenates of A. variabilis, there was no evidence of any desaturase activity.